.img files?

I'm confused re.

gmapbmap.img
gmapprom.img
gmapsupp.img

gmapprom is the default mapset (ie, for your home country)?

gmapbmap is "base map"? Surely this isn't a complete detailed map: the file
size is only 15 percent of the other .img files. Why so small? What is a
"base map" and how does it differ from a mapset?

gmapsupp is secondary mapset? If, for example, you want to visit another
country you can load a map onto an SD card and name it gmapsupp.img?

Which of these are required; which are optional?

Is my understanding correct?

Tx.

here's a re-post of mine - from Jan 2010

BTW - You might indicate what GPS you have,
and what maps are listed in your "About" screen.

---
After a recent map update to my Garmin Nuvi 255 GPS,
I looked at the GPS sub-dir to see how big the map image file was...

In looking around the GPS sub-dir,
I noticed a couple of other different files....
These appear to be the new TimeZone files -


SO - this is my D:Garmin sub-dir of map info


gmaptz.img Time Zone map info
gmaptz.sum


gmapbmap.img 92mb - basemap
gmapbmap.sum


gmapprom.img 1.1gb - latest CNNT 2010.30
gmapprom.unl guessing map unlock code
gmapprom.sum


gmapsupp.img 19mb - my topo map segments

So, which are required and why?

And why is a "basemap" only 92mb and the primary mapset is 10x that? What's
in each? Are both needed?

Thanks.

==

Well - you can pretty much delete what you want,
and then you'll have no maps - and a pretty useless GPS :)

Why are you asking about deleting things ?
Are you looking to delete to save space or what ?

You replied that you have a Garmin 660 -
BUT - What "maps" do you have installed ?
We have no idea what products you have purchased
or installed on your GPS - and each will create a file,
or a set of files...

Basemap - very basic map image with nothing else
Purchased maps - add more map details and POIs for reference/lookup.

What's the purpose of a basemap? You can't select a it. Is it only defaulted
to if no purchased mapset is installed? Does it become optional if a gmapprom
or gmapsupp file is installed? Can this be deleted if a purchased mapset is
installed?

I don't like files sitting around (on my computer or GPS) that aren't needed.
And this leaves more room for MP3's, audio books, POI's, etc.

Installed: NA mapset including USA & Canada

Planning on getting Europe too.